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From "Jukka Zitting (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (JCR-3555) Add a static utility to transform JCR Iterators into Iterables
Date Wed, 03 Apr 2013 08:37:16 GMT

    [ https://issues.apache.org/jira/browse/JCR-3555?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13620735#comment-13620735
] 

Jukka Zitting commented on JCR-3555:
------------------------------------

Perhaps something like this:

    public class OneShotIterable<T> implements Iterable<T> {

        private final boolean first = true;

        private final Iterator<T> iterator;

        public OneShotIterable(Iterator<T> iterator) {
            this.iterator = iterator;
        }

        @Override
        public synchronized Iterator<T> iterator() {
            if (first) {
                first = false;
                return iterator;
            } else {
                throw new IllegalStateException(
                    "Unable to iterate more than once over a single iterator");
            }
        }

    }
                
> Add a static utility to transform JCR Iterators into Iterables
> --------------------------------------------------------------
>
>                 Key: JCR-3555
>                 URL: https://issues.apache.org/jira/browse/JCR-3555
>             Project: Jackrabbit Content Repository
>          Issue Type: Improvement
>          Components: jackrabbit-jcr-commons
>    Affects Versions: 2.6
>            Reporter: Lukas Eder
>            Priority: Minor
>         Attachments: Iterators.java.patch
>
>
> I have stumbled upon the utility classes in the org.apache.jackrabbit.commons.iterator
package. They're quite useful in principle, but not applied thoroughly. E.g. there are missing
wrapper types for at least these JCR Iterators:
> - AccessControlPolicyIterator
> - EventIterator
> - EventListenerIterator
> - NodeTypeIterator
> - VersionIterator
> Instead of adding more classes, it might be useful to create static methods for the job.
Using static methods from a single class (with static imports) is a bit more convenient than
looking up and creating the wrapper types using "new WrapperType(...)"
> An example:
> org.apache.jackrabbit.commons.iterator.Iterators.iterable
> // And then:
> for (Node n : iterable(parent.getNodes())) {
>   // Do stuff with n
> }
> Please find attached a .patch file containing an implementation suggestion.

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